We propose to study the independent and combined effects of 9 months of endurance exercise training and hormone replacement therapy (HRT) on left ventricular (LV) size and function on arterial stiffness in 60 to 72 yr-old women. Maximal cardiac output will be measured by the acetylene rebreathing procedure. LV size and function will be assessed by 2-d echocardiography and Doppler ultrasound under basal conditions and during alpha and beta adrenergic stimulation induced by phenylephrine and isoproterenol, respectively. Arterial stiffness will be evaluated by measuring the pulse wave velocity.